City Comptroller William Thompson was delinquent on property taxes for a year on land and a house in Massachusetts he inherited from his mother, documents reviewed by The Post reveal.

Thompson, the leading Democratic hopeful for mayor, owed roughly $4,800 on the three pieces of land in Barnstable, Mass., for taxes since mid-year 2008, property records show.

Two of the three pieces of land are adjacent, and there is a three-bedroom house on one of them, which was willed to the comptroller and his sister when their mom passed away last year, his office has said.

The quarterly tax bills started getting missed as of August 2008, and records through May show they were still unpaid, to a tune of about $4,800.

The combined properties have an assessed value of several hundred thousand dollars.

It wasn’t clear yesterday to what address the tax bills were sent, but Barnstable annual reports show that between 2000 and 2008, the tax bills for all three pieces of land were sent to 768 Putnam Ave. in Brooklyn, a house where Thompson lived during that time.

Contacted by The Post, Thompson spokesman Jeff Simmons said: “All taxes on the comptroller’s deceased mother’s estate had been paid by the comptroller’s sister in July.”

He declined to explain why they were delinquent or to provide an exact payment date and amount, saying only that relatives had agreed they would be paid by the sister.

“Over the last year since Bill’s mother passed away, his family has been settling her affairs,” he added. “The fact is, the comptroller’s family has paid the taxes, and did so in July.”

He insisted the deeds for the properties haven’t yet been transferred to Thompson and his sister.

The Post recently reported that Thompson planned to update his Conflicts of Interest Board filings to reflect the fact that he co-owned one of the parcels since 1980.

His aides said he had always considered it his mother’s and it had been an accidental omission from his filings.

The address in Brooklyn where the tax bills for Massachusetts were sent was Thompson’s family home, Simmons said. He also said Thompson’s mother had been living there for at least some of the time between 2000 and her death.

Still, having outstanding tax bills could create a troublesome appearance for the city’s chief fiscal officer, who has been gaining on Mayor Bloomberg in the polls and is within 10 points as the race hits the crucial final weeks.

Thompson also owns a home in Harlem with his third wife, and his first wife pays rent on an apartment in the Brooklyn home.

The Massachusetts properties qualify as other real estate besides his primary or secondary residences.